The hepatitis C virus (HCV) is the leading cause of chronic liver disease worldwide (Boyer, N. et al. J Hepatol. 32:98-112, 2000) so a significant focus of current antiviral research is directed toward the development of improved methods of treatment of chronic HCV infections in humans (Di Besceglie, A. M. and Bacon, B. R., Scientific American, October: 80-85, (1999); Gordon, C. P., et al., J. Med. Chem. 2005, 48, 1-20; Maradpour, D., et al., Nat. Rev. Micro. 2007, 5(6), 453-463). A number of HCV treatments are reviewed by Dymock et al. in Antiviral Chemistry & Chemotherapy, 11:2; 79-95 (2000). Virologic cures of patients with chronic HCV infection are difficult to achieve because of the prodigious amount of daily virus production in chronically infected patients and the high spontaneous mutability of HCV virus (Neumann, et al., Science 1998, 282, 103-7; Fukimoto, et al., Hepatology, 1996, 24, 1351-4; Domingo, et al., Gene, 1985, 40, 1-8; Martell, et al., J. Virol. 1992, 66, 3225-9).
Primarily two compounds, ribavirin, a nucleoside analog, and interferon-alpha (α) (IFN), have been used to treat chronic HCV infections in humans. Ribavirin alone is not effective in reducing viral RNA levels, has significant toxicity, and is known to induce anemia. The combination of IFN and ribavirin has been reported to be effective in the management of chronic hepatitis C (Scott, L. J., et al. Drugs 2002, 62, 507-556) but less than half the patients given this treatment show a persistent benefit. Recently, both telaprevir and boceprevir have also been approved in the United States for the treatment of HCV.
Additionally, alkynyl substituted thiophenes with anti-Flaviviridae virus activity have been disclosed by Chan, et al., WO 2008058393; Wunberg, et al., WO 2006072347; and Chan, et al., WO 2002100851; but none of these are currently approved as antiviral therapeutics. In spite of the above described reports, infections from the Flaviviridae virus family, including HCV, continue to cause significant mortality, morbidity and economic losses throughout the world. Therefore, there remains a need to develop effective treatments for Flaviviridae virus infections (e.g. HCV). In particular, there is a need for treatments for Flaviviridae virus infections that have developed resistance to one or more of the currently available therapies.